This invention relates to a seal apparatus for a water pump and a rotation-support apparatus for a water pump and a water pump, and more particularly to improvement of the seal apparatus of a water pump that is used for circulating coolant water for an automobile engine.
A water pump used for circulating coolant water for an automobile engine has been disclosed in Japanese Patent Publication No. Toku Kai Hei 8-254213, and is constructed as shown in FIG. 6. A cylindrical housing 1 has an installation flange 2 formed around its outer peripheral surface on the axial inside end (the inside with reference to the axial direction is the side nearest the engine, and is the right side in all of the figures) and fastened to the cylinder block of the engine by way of the installation flange 2. Provided on the radial inside of the housing 1 is a rolling-bearing unit 6 which comprises a ball bearing 4 on the axial inside end and a roller bearing 5 on the axial outside end (the outside with reference to the axial direction is the side furthest from the engine, and is the left side in all of the figures) in combination to support a rotating shaft 3 such that it rotates freely on the radially inside of the housing 1. There are seal rings 7, 7 located on both ends in the axial direction (left and right direction in FIG. 6) of this rolling-bearing unit 6 that prevent the grease filled inside the bearing unit from leaking out, as well as, prevent foreign matter such as dirt or steam on the outside from getting inside the unit. Moreover, a pulley 8 is fastened to a section on the outside end of the aforementioned rotating shaft 3 that protrudes from the opening on the outside end of the housing 1.
When installed in the engine, a belt (not shown in the figure) is placed around this pulley 8, and it rotates and drives the aforementioned rotating shaft 3 from the crankshaft of the engine. On the other hand, an impeller 9 is fastened to a section on the inside end of the rotating shaft 3 that protrudes from the surface on the inside end of the installation flange 2. When this installation flange 2 is fastened to the cylinder block of the engine, the aforementioned impeller 9 goes inside the water jacket that is formed within this cylinder block. As the rotating shaft 3 rotates, the coolant water inside the water jacket is circulated to and from a radiator (not shown in the figure) or that like.
Furthermore, there is a mechanical seal 10 located between the outer peripheral surface of the rotating shaft 3 and the inner peripheral surface of the housing 1. When the engine is operating, this mechanical seal 10 allows rotation of the rotating shaft 3 while at the same time prevents steam or coolant water that is flowing inside the water jacket, from leaking out. However, with the aforementioned mechanical seal 10, obtaining a perfect seal is difficult, and when friction heat is generated on the seal surface of this mechanical seal 10, the coolant water, which contains chemical matter such as an anti-freeze agent or anti-rust agent, evaporates and becomes steam and leaks out toward the rolling-bearing unit 6, while at the same time, the coolant water in which the aforementioned chemical matter is condensed due to evaporation of the coolant water and also leaks out to the rolling-bearing unit 6. Therefore, a slinger 11 is located in the middle of the rotating shaft 3 between the mechanical seal 10 and the inside seal ring 7, and a supply-discharge hole (not shown in the figure) is formed in the middle of the housing 1 in the section that faces the outer peripheral edge of the slinger 11, which allows the steam or hot water that leaked out from the mechanical seal 10 to freely be discharged outside the housing 10. In other words, the aforementioned supply-discharge hole is provided for communication between the outside and a space which is located between the mechanical seal 10 and the inside seal ring 7 in the axial direction to act as a steam chamber, so that the steam and hot water in this space are discharged to the outside.
In the first example of prior art construction shown in FIG. 6, the inner peripheral edge of a pair of seal lips 12, 12 of the inside seal ring 7 comes in sliding contact all the way around the outer peripheral surface in the middle of the rotating shaft 3. The inside seal ring 7 and aforementioned slinger 11 are not associated with and are independent of each other.
With respect to this, as shown in FIG. 7, Japanese Patent Publication No. Toku Kai Hei 11-153096 discloses a construction for improving the seal performance by locating the seal ring 7a and slinger 11a such that they are associated with each other. In the case of this construction, two of the three lips 12a, 12b and 12c of the seal ring 7a, specifically the seal lips 12a and 12b come in sliding contact all the way around the outer peripheral surface of the rotating shaft 3a. On the other hand, the edge of the remaining seal lip 12c comes in sliding contact all the way around the outside surface of the slinger 11a. With this kind of construction, the seal performance is improved over the first example of prior art construction shown in FIG. 6, and it is possible to more effectively prevent foreign matter such as steam or hot water from getting inside the rolling-bearing unit that supports the rotating shaft 3a. 
Moreover, similar to the construction of this invention described later, it is considered that an outer-diameter-side cylindrical section is formed on the outer peripheral edge of the slinger such that it is concentric with the rotating shaft, and that a seal lip is provided with a tip edge such that it is inclined inward in the radial direction toward the tip edge, and that the tip edge comes in sliding contact with the outer peripheral surface of this outer-diameter-side cylindrical section. With this kind of construction, since foreign matter collects on the outer peripheral surface of the aforementioned outer-diameter-side cylindrical section where there is a large centrifugal force due to the large diameter, it is efficiently thrown off by this centrifugal force. Therefore, it is possible to even more effectively prevent foreign matter such as steam or hot water from getting inside the rolling-bearing unit.
In the case of a second example of prior art construction shown in FIG. 7 and in the case of construction where the tip edge of the seal lip comes in sliding contact with the outer peripheral surface of the outer-diameter-side cylindrical section that is formed around the outer peripheral edge of the slinger, the seal is better than the first example of prior art construction shown in FIG. 6. However, in order to be able to effectively prevent foreign matter from getting into the bearing unit over a long period of time, further improvement is desired. In other words, in the case of the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 11-153096 as shown in FIG. 7, only the construction in which the edge of one of the three seal lips 12a, 12b and 12c of the seal ring 7a, that is of the seal lips 12c, comes in sliding contact with the outside surface of the slinger 11a is mentioned, however detailed specifications are not given.
With respect to this point, in order to be able to effectively prevent foreign matter from getting into the bearing unit over a long period of time, it is necessary to satisfy the following conditions (1) and (2).
(1) The tip edge of the seal lip 12c must come in sliding contact all the way with the outside surface of the slinger 11a with sufficient pressure and with no gaps.
(2) Wear of the tip edge of the seal lip 12c due to rubbing with the outside surface of the slinger 11a must be kept to a minimum.
In the case of satisfying only condition (1) above, it is possible to increase the amount of elastic deformation of the seal lip 12c and increase the force to push the tip edge of the seal lip 12c against the outside surface of the slinger 11a. On the other hand, in the case of satisfying only condition (2) above, it is possible to reduce the amount of elastic deformation of the seal lip 12c and decrease the force to push the tip edge of the seal lip 12c against the outside surface of the slinger 11a. 
Since the condition (1) above for securing the seal performance is counter to the condition (2) above for securing durability in this way, actual construction for effectively preventing foreign matter from getting inside the bearing unit over a long period of time is very important.
It is an objective of this invention to provide a seal apparatus for a water pump, rotation-support apparatus for a water pump and a water pump, taking the aforementioned problems into consideration.
Of the seal apparatus for a water pump, rotation-support apparatus for a water pump and water pump of this invention, the seal apparatus for a water pump as disclosed in the claims comprises a seal ring provided to block the space between the inner peripheral surface of a non-rotating member, and the outer peripheral surface of the rotating shaft of the water pump that passes through this non-rotating member, the outer peripheral edge of the seal ring being fastened to the inner peripheral surface of the non-rotating member, and a slinger that is fitted around the rotating shaft. Moreover, there is an outer-diameter-side cylindrical section that is formed around the outer peripheral edge of the slinger such that it is concentric with the rotating shaft. Also, the seal ring comprises a first seal lip that comes in sliding contact with an outer peripheral surface of the rotating shaft or with an outer peripheral surface of the slinger that rotates together with the rotating shaft, and a second seal lip that comes in sliding contact with an outer peripheral surface of the outer-diameter-side cylindrical section and that is tilted inward in the radial direction toward the tip edge.
Moreover, the rotation-support apparatus for the water pump as described in the claims comprises: an outer ring having an outer-ring raceway formed around its inner peripheral surface; a rotating shaft for the water pump having an inner-ring raceway formed around its outer peripheral surface; a plurality of rolling elements located between the outer-ring raceway and inner-ring raceway such that they can rotate freely; a seal ring whose outer peripheral edge is fastened to the inner peripheral surface on the end of the outer ring; and a slinger that is fitted around the rotating shaft. Moreover, there is an outer-diameter-side cylindrical section that is formed around the outer peripheral edge of the slinger such that it is concentric with the rotating shaft. Also, the seal ring comprises a first seal lip that comes in sliding contact with an outer peripheral surface of the rotating shaft or with an outer peripheral surface of the slinger that rotates together with the rotating shaft, and a second seal lip that comes in sliding contact with an outer peripheral surface of the outer-diameter-side cylindrical section and that is tilted inward in the radial direction toward the tip edge.
Furthermore, the water pump described in the claims comprises: a housing; an outer-ring raceway that is formed directly around the inner peripheral surface of this housing or formed around a separate outer ring around the inner peripheral surface of this housing; a rotating shaft having an inner-ring raceway that is formed around its outer peripheral surface; a plurality of rolling elements that are located between the outer-ring raceway and inner-ring raceway such that they roll freely; a seal ring whose outer peripheral edge is fastened to the inner peripheral surface on the end of the outer ring; a slinger that is fitted around the rotating shaft; a pulley that is fastened to the outside end of the rotating shaft; an impeller that is fastened to the inside end of the rotating shaft; a mechanical seal that is located between the inner peripheral surface of the housing and the outer peripheral surface of the rotating shaft in the section between the impeller and the slinger in the axial direction; and a space that is located between the mechanical seal and the seal ring in the axial direction. Moreover, there is an outer-diameter-side cylindrical section that is formed around the outer peripheral edge of the slinger such that it is concentric with the rotating shaft. Also, the seal ring comprises a first seal lip that comes in sliding contact with an outer peripheral surface of the rotating shaft or with an outer peripheral surface of the slinger that rotates together with the rotating shaft, and a second seal lip that comes in sliding contact with an outer peripheral surface of the outer-diameter-side cylindrical section and that is tilted inward in the radial direction toward the tip edge.
Particularly, in the case of the seal apparatus for a water pump, the rotation-support for a water pump and the water pump of this invention, the amount of elastic deformation of the second seal lip, which occurs when the tip: edge of the second seal lip comes in contact with the outer peripheral surface of the aforementioned outer-diameter-side cylindrical section, is at least {fraction (1/10)} and up to {fraction (7/10)} the height of the second seal lip in the free state. In addition, the roughness of the section of the outer peripheral surface of the outer-diameter-side cylindrical section which the tip edge of the second seal lip comes in sliding contact with is from 0.2 xcexcm to 2.0 xcexcm in the arithmetic mean Ra, or is from 0.8 xcexcm to 8.0 xcexcm in the maximum height Ry.
Preferably, the amount of elastic deformation of the second seal lip is at least {fraction (2/10)} and up to {fraction (5/10)} the height of the second seal lip in the free state, and even more preferably at least {fraction (2/10)} and up to {fraction (3/10)} the height in the free state.
Moreover, the cross-sectional shape of the second seal lip is preferably a wedge shape in which the width (thickness) dimension becomes smaller going from the base end to the tip end. At the same time, the length dimension of the second seal lip is at least two times than the average thickness dimension of second seal lip, and preferably at least 2.5 times.
With the seal apparatus for a water pump, the rotation-support for a water pump and the water pump of this invention, constructed as described above, it is possible to effectively prevent foreign matter from getting inside the rolling-bearing unit that supports the rotating shaft of the water pump over a long period of time.